I built a deer gun from the ground up. The parts aren't that hard to assemble, I don't need a gunsmith to tell me how it functions, as I've used one 22 years free from Uncle Sam. It did teach me things about the AR they either never said or I already forgot.

For hunting, launching the bullet is what it's all about, like fishing, once on the hook, what the label on the reel says isn't very important to the fish. Most uppers and lowers are basically a commodity item, you decide how much of a premium you're willing to pay for a rollmark, and maybe what color anodizing. I bought an AGP lower and blem LAR upper, with less than $150 in BOTH. Shop it, you can beat that with a known quality vendor. It just won't have the internet commando's seal of acceptance on it.

Caliber, barrel, gas length, then upper, stock, grip, forearm, last trigger. If you are building for deer, then the effective maximum range is 300m. At 50-60 yards - which is average for a lot of whitetail hunting, 5.56 will do the job. I choose 6.8, to carry 40% MORE power downrange, and reduce the number of poor shots letting game get away. I've lost deer to other hunters with a .30-06, shot placement is important - so my focus is on accurate fast first shots, and accurate fast followup shots. Whitetails don't pose for hunters, and one more bullet in them can make a serious difference. Scoped bolt guns are popular here, I lost that deer using one, and I can tell you many others blaze away with them, too. The recoil and loading work against you. I won't do it again.

I choose 16" as 6.8 was designed for 14.5", and that's already long enough. Midlength gas is appropriate for 16". The upper was A3 for the optic rail, red dots are my #1 deer optic since 1978 because you can get on target quicker without hunting for the game or which end you're aiming at. In the 50-200 yard range, a 3X scope hinders the hunter more than helps. Stock, simple A1 as the length of pull works for me in winter clothing, and I can still shoot nose to the charging handle. Grip was a TD Battlegrip for size - buy the right one first and avoid the little parts on the multisized ones. Grip emphasis on a two handed weapon supported at the shoulder is overdone. I put a rifle handguard on it to extend my support hand and protect it from a cold barrel - or hot one at the range. The front sight got mounted dissipator, and I don't have fiddle with them to use it, they're up and available if poor conditions or the optic doesn't work. The issue sights are also $120 cheaper than BUIS, and I didn't have to pay $250 for a front sight mount - also known as a quad rail. Free floats DON'T make barrels more accurate, they just keep sling tension off the barrel. If you hunt in a tree stand or blind, you likely don't use a sling as it limits you moving to sight in on the target. 2MOA is all you need for hunting anyway - that's an 8" circle at 400m, and most of us can't see deer that far out anyway. Terrain and vegetation severely limit our visual ability.

I put the trigger last because most hunting and target triggers use an adjustable take up screw to limit creep. The AGP lower came with one installed, it cut about 65% of it, and made it as good as the trigger on my Win 94 and Rem 700. I don't like superlight target triggers on guns, as my hunting is on rough terrain with lots of underbrush - just like field conditions in the Army, who already discovered 6-8 pounds is the safe threshold for tired soldiers. At the end of a long day - hunting or when I was in training over 22 years - negligent discharges aren't the answer to the bragging rights of owning a $250 trigger. Especially when a $40 add on screw can do almost as well, and safely.

An M4gery could do ok as a deer rifle, I've selected my parts to do the job better for me, based on my experience for what I need. Noisy adjustable stocks and short handguards aren't optimum for what I have in mind, and neither was a varmint cartridge. 6.8SPC carries the minimum 1000 foot pounds of energy beyond 300 yards easily, it don't have to accept deliberately cutting off my shots, or question whether it's good enough at the limit of my ability. What I have to work on is getting the right shot while I can first, and not worrying about any limitations with the gun. For what it does, it's already proven as a great cartridge and more than what many would expect in the size of gun offered.